Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S967322AbWKZHUs (ORCPT ); Sun, 26 Nov 2006 02:20:48 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S967326AbWKZHUs (ORCPT ); Sun, 26 Nov 2006 02:20:48 -0500 Received: from shawidc-mo1.cg.shawcable.net ([24.71.223.10]:53136 "EHLO pd4mo3so.prod.shaw.ca") by vger.kernel.org with ESMTP id S967322AbWKZHUr (ORCPT ); Sun, 26 Nov 2006 02:20:47 -0500 Date: Sun, 26 Nov 2006 01:20:46 -0600 From: Robert Hancock Subject: Re: [patch] x86: unify/rewrite SMP TSC sync code In-reply-to: To: linux-kernel Cc: Wink Saville , Arjan van de Ven Message-id: <4569404E.20402@shaw.ca> MIME-version: 1.0 Content-type: text/plain; charset=ISO-8859-1; format=flowed Content-transfer-encoding: 7bit References: User-Agent: Thunderbird 1.5.0.8 (Windows/20061025) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1387 Lines: 37 Wink Saville wrote: > Arjan van de Ven wrote: >>> Actually, we need to ask the CPU/System makers to provide a system wide >>> timer that is independent of the given CPU. I would expect it quite >>> simple >> >> they exist. They're called pmtimer and hpet. >> pmtimer is port io. hpet is memory mapped io. > > Thanks for the info. I took a look at Documentation/hpet.txt and > drivers/char/hpet.c > and see that hpet_mmap is implemented in the driver but nothing hpet.txt > indicates > what is being mapped. > > Could you point me to any other documentation? I did find the following: > > http://www.intel.com/hardwaredesign/hpetspec_1.pdf > > Are you aware of any example user code that uses the mmap capability of > hpet? Generally user mode code should just be using gettimeofday. When the TSC is usable as a sane time source, the kernel will use it. When it's not, it will use something else like the HPET, ACPI PM Timer or (at last resort) the PIT, in increasing degrees of slowness. -- Robert Hancock Saskatoon, SK, Canada To email, remove "nospam" from hancockr@nospamshaw.ca Home Page: http://www.roberthancock.com/ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/